Along with the development of a wireless multimedia service, people have increasing requirements on high data rate and user experiences, so that higher requirements on system capacity and coverage of a conventional cellular network are made. On the other aspect, due to wide application of applications such as a social network, short-distance data sharing and local advertisement, requirements of people on proximity services gradually increase. A conventional base-station-centred cellular network has obvious limitations to high data rate and proximity service supporting, and under such a requirement background, a Device-to-Device (D2D) technology representative of a new development direction of a communication technology in the future emerges. With the application of the D2D technology, a burden of a cellular network may be reduced, battery power consumption of UE may be reduced, a data rate may be increased, robustness of a network infrastructure may be improved, and requirements of high-data-rate services and proximity services may be well met.
A D2D technology may work in an authorized frequency band or an unauthorized frequency band, and allows direct discovery and/or direct communication of multiple pieces of D2D UE under a condition of presence of network infrastructure or absence of the network infrastructure. The following three main D2D application scenarios exist:
1): UE1 and UE2 perform data interaction under coverage of a cellular network, user plane data does not pass through network infrastructure, and the application scenario is specifically implemented as shown by mode 1 in FIG. 1;
2): UE in a poorly covered/uncovered area performs relay transmission, and the application scenario is specifically implemented as shown by mode 2 in FIG. 1, that is, UE4 with poorer signal quality is allowed to communicate with a network through UE3 covered by the network in the vicinity, thereby helping an operating company to enlarge a coverage area and improve system capacity; and
3): under the condition that a cellular network may not work normally in case of earthquake or emergency, direct communication among equipment is allowed, and as shown by mode 3 in FIG. 1, UE5, UE6 and UE7 perform one-hop or multi-hop data communication in a manner that communication between the control plane data and user plane data does not pass through the network infrastructure.
A D2D technology usually includes a D2D discovery technology and a D2D communication technology, wherein the D2D discovery technology refers to a technology used to judge/determine that two or more pieces of D2D UE are adjacent (for example, within a direct D2D communication range) or used to judge/determine that first UE is adjacent to second UE. D2D UE may usually be discovered by each other by sending or receiving discovery signals/information, and under the condition of presence of cellular network coverage, the D2D discovery of the D2D UE may be assisted by a network; and D2D communication technology refers to a technology capable of realizing direct communication in a manner that a part or all of communication data between the D2D UE does not pass through network infrastructure.
At present, a main D2D discovery method includes that D2D UE (first UE) sends identity information capable of identifying the D2D UE which sends the discovery information, and discovery-end D2D UE (second UE) performs corresponding D2D UE identity information searching and identifies the received D2D identity information, thereby finishing a D2D UE discovery process. However, because of diversity of D2D communication modes, it may be difficult to meet a requirement on D2D communication diversity by only including identity information in a discovery message.
The abovementioned flow is easy to implement, but it is not enough to only contain identity information in discovery information in consideration of various D2D communication modes mentioned before.
For the problem, there is yet no effective solution.